class Solution {
public:
    void push(int node)
    {
        stack1.push(node);
    }
    int pop()
    {
        while (!stack1.empty())
        {
            stack2.push(stack1.top());
            stack1.pop();
        }
        int res = stack2.top();
        stack2.pop();
        while (!stack2.empty())
        {
            stack1.push(stack2.top());
            stack2.pop();
        }
        return res;
    }

private:
    stack<int> stack1;
    stack<int> stack2;
};